Monday, August 22, 2016

We are one-year away from the Solar Eclipse that will be visible across the United States on August 21st, 2017. I was watching the weather this past week to see where the best locations -- the most cloud-free spots-- would be, IF the eclipse had occurred this August.

A few days ago, there were clouds in the path over parts of Idaho & Wyoming, most other locations to the east and west (in the western half of the United States) were relatively clear. The day before, some high thin clouds and contrails were present around noontime in western Wyoming.

However, on Sunday the 21st of August 2016, skies were generally
cloud-free along that entire path of the eclipse, from Oregon to western Nebraska.
Although, there was plenty of smoke and haze to be found in parts of Idaho,
Wyoming & Oregon from large forest fires that have been on-going
this past month.

If you zoom-in, you can actually see some of the smoke plumes on the visible
satellite photo taken in the afternoon on Sunday, August 21, 2016.

For next August, it would be ideal to see a repeat of the sky conditions along the path, but without the fires to dim the show.

Friday, August 5, 2016

(Note: the content of this post first appeared in the MountainWeather column in the Jackson Hole News & Guide on July 20, 2016).

Every
summer I feel obliged to reiterate a few important points about lightning
safety. Maybe this will be your first time hearing this message, or maybe an
annual reminder isn’t such a bad thing.

In a previous post, I outlined what to watch for, as far as cumulus clouds
developing into a potential thunderstorm. Vigilantly observing the sky
throughout the day is the first step towards knowing when it is time to retreat
from the mountains, get off the lake, or the local ball fields.

In this post,
I will cover what to do when thunderstorms are imminent, and Mother Nature says
it’s “game-on” for dangerous lightning.

Lightning
Facts

Most people
are not killed by a direct hit from a lightning bolt. Although, that certainly would
do the job and be “game over”, right there. More commonly, people are injured
or killed when lightning strikes nearby, causing an instantaneous surge of
electrical current, and intense heat, known as a “side-flash”.

The most
common cause of lightning casualties, however, comes from getting shocked by
the high voltage current that runs through the ground. Ground current accounts
for about 50-percent of all lightning casualties.

Look at it
this way; a lightning bolt is like a hand-grenade going off. Standard
Army-issue hand grenades have a kill-radius of about 25-feet, and a
casualty-radius of about 50-feet. Therefore, getting to a safe, or safer
location, where lightning is less likely to hit is your next line of defense.

Seek
Shelter Early

As soon as
you can hear the thunder, lightning is close enough to strike, and it is time
to seek shelter. Lightning bolts can be seen from about 15 miles away, and
thunder can be heard up to about 10 miles away, on a good day. In a canyon, out
in the wind, or at a noisy concert, thunder may not be heard until it is much
closer.

You can
estimate how far away the lightning is by counting the time between when you
see the flash of lightning and when you hear the thunder. Count in seconds
(one-thousand-one, one-thousand two, etc.). Five seconds equals one mile. If
you count to 25, that means the lightning is 5 miles away, which is actually close
enough to be able to reach out and touch you.

Don’t wait
for it to start raining before you think about seeking shelter, or for the
first bolt to hit nearby, as most people tend to do.

Inside a
building or a car are the absolute safest places to be. Picnic shelters, a
gazebo, a dugout at the ball field, are NOT good shelters from lightning.

If you are
out on a hike, don’t run underneath the biggest, loneliest looking tree for
shelter, as most people also tend to do, especially once it starts raining. A
better option is to get into a group of trees of similar height. Also, make
sure you are not standing on top of any tree roots.

If all else
fails, get into a low spot in the terrain, that is not a watercourse, and crouch
down. Like Army guys do when they dive into a bunker to avoid the grenade’s
blast.

If you are
in the mountains, do whatever you can, as fast as you can, to get off the
higher ridgetops. Waiting it out in a gully or low spot between ridges is
better than nothing, but avoid a gully that might become a running watercourse
when the downpour starts. And separate yourself from all metal objects, ice
axes, climbing hardware, etc.

Also, DO
NOT get under an overhanging rock or in a cave. Electricity will often jump the
gap that you are sitting or standing in when lightning strikes nearby.

If you are
on a lake or river, get out of the water and off the boat. Water is a great
conductor of electricity! Get to shore and find a stand of similar sized trees
to wait it out.

The
absolute best thing you can do to prevent injuries from lightning striking nearby
is: KEEP YOUR FEET TOGETHER.

Standing
with both feet together will help prevent dangerous ground currents from
running up through one leg and exiting down the other. You may feel a bump
under your feet as the ground current passes, if both feet are together, but it
is unlikely that you would receive a serious electrical injury.

Secondarily, don’t huddle together in a group. Spread out, at
least 25-feet feet apart, if not 50-feet apart, so everyone is not within the
same kill/casualty radius. Cows and sheep tend to huddle together during
thunderstorms, and often entire herds or flocks are killed because they are all
linked together as one big conductor of electricity.

It is best to remain in a safe location for 20 to 30 minutes
after the last of the lightning leaves the area; to make sure that the
thunderstorm is a safe distance away. It is really hard to convince people to
wait a little longer. We usually run right back out to play as soon as the rain
stops.

Pay attention to the weather forecast each day, to see what
the probability of thunderstorms might be. Be observant of the clouds as they
develop during the day. And don’t wait until the lightning is flashing or the
rain is pouring to turn around and head for a safer location.

Jim
is the chief meteorologist at mountainweather.com
and has been forecasting the weather in Jackson Hole
and the Teton Mountains for almost 25 years.

(Note: The content in this post first appeared in the MountainWeather column in the Jackson Hole News & Guide on July 6th, 2016).

July begins the heart of the “Thunderstorm Season” in the Rockies. It is also the peak of the tourist season, climbing, backpacking, & baseball seasons, etc. etc. . That means more
people will be outdoors enjoying the weather, and potentially getting caught in
thunderstorms.

In this post I will describe how thunderstorms work,
and what to watch for when you are outside during the day. Those telltale
signs that dangerous thunderstorms may be developing. I will
follow this post with a subsequent one on lightning safety.

Moist and
Unstable Air

Most of us would
probably describe a “typical summer day” as: Clear blue skies in the morning, followed
by some puffy cumulus clouds in the afternoon, and maybe a chance of some
afternoon thunderstorms.

How big or
ominous those cumulus clouds become will depend on two things:
1) How much moisture is in the air. 2) How unstable the air is.

That clear
blue sky that you see in the morning actually contains some moisture, in the
form of invisible water vapor. As the day goes on, and the ground heats up, the
air begins to rise. As the warmer air rises higher into the atmosphere it
encounters colder temperatures, and the invisible water vapor condenses into visible
water droplets.

If the air
keeps rising, cooling, and condensing, then water droplets start to gather
together, and clouds appear.

Relative
humidity (RH) is one way to measure how moist the atmosphere is. For
thunderstorm development, it can still be very dry in the lower levels of the
atmosphere, with low RH. But at the same time, high RH may exist in the upper
levels of the atmosphere, which is enough to perk up thunderstorms once there
is enough instability.

How
unstable the atmosphere is will depend on the difference in temperature between
the ground and the upper levels, like up around 20 to 25,000-feet. The bigger
the difference in temperature, the more unstable the air is, that is, it must
be warmer down low and colder up high to be unstable. Think, “hot air rises”,
that’s instability.

If the air
isn’t rising, or if temperatures aren’t very cold aloft, or the atmosphere is
staying bone dry up through 25,000-feet, then all we see is clear blue skies,
all day.

Be Observant

There are a
few things to keep an eye on to determine if those little white puffy clouds
are going to develop into full-blown thunderstorms on any given day. Watch the
sky for these signs of impending thunderstorms:

3) The base
of the cloud gets darker, indicating the clouds are growing taller.

4) Taller
clouds, darker bases and more of the sky covered by those clouds, the greater
the potential for heavy rainfall, hail, and/or strong gusty downdraft winds.
And of course, lightning.

However, don’t
be lulled into thinking that clouds and thunderstorms can only develop during
the afternoon hours. There are many days that don’t fit this “typical” summertime
thunderstorm scenario.

Thundertorm
Enhancers

Storm
systems, otherwise known as low-pressure systems, will periodically roll across
the Rockies in the summer, and these will add additional moisture &
instability to the atmosphere.

Often associated
with a low-pressure system, is a “cold front”. Cold fronts produce more lift
and give a boost to the instability. Some of the more potent and violent
thunderstorms we see are directly related to the passage of a cold front.

The last
thing to be aware of is, the “summer monsoon”. In brief, the Desert Southwest
Monsoon is a seasonal wind flow pattern that brings very moist and unstable air
up from central Mexico, across the Four-Corners Region, and sometimes that
monsoon moisture gets circulated as far north as Northwest Wyoming.

Thunderstorms
associated with the monsoon are some of the most random that we will see in the
summer, and can occur any time of the day or night.

Whenever
you experience a thunderstorm in the middle of the night or just after sunrise
– when the afternoon heating is not really a factor– it is very likely that a
storm system, a cold front, or the monsoon is triggering the thunderstorm activity.

Keeping an
eye on thunderstorm development is of paramount importance to anyone who is
spending the day outside. If the clouds develop into lightning-producing
thunderstorms, then you are at risk of being injured or killed by a lightning
strike; whether you are climbing the Grand, playing a around of golf, fishing the
river, or out on the lake or ball field.

Jim is the
chief meteorologist at mountainweather.com and has been forecasting the weather
in Jackson Hole and the Teton Mountains for almost 25 years.

(Note: Content in this post first appeared in the MountainWeather column in the Jackson Hole News & Guide June 8, 2016)

Sometimes, the forecast can be confusing or misleading,
especially when it comes to understanding the “probability of precipitation. In
this week’s column I will explain what those percentages really mean, by way of
analogy.

Weather Doctor

Being a meteorologist is a lot like being a doctor, except that
my patient is the atmosphere. That patient shows up in my office everyday with
a different set of symptoms and ailments. My task is to analyze what is wrong
with my patient.

I begin my assessment by looking at satellite and radar
images, along with a host of weather maps and observations to get some baseline
information. Kind of like the nurse taking your vitals and patient history.

Next, I try and diagnose the problem (or problems) the
atmosphere might be presenting to me. I look for the obvious signs and symptoms
first. Some days they may be so obvious that the diagnosis is relatively
simple. For instance, if it is already pouring rain and thunder-storming
outside, then the forecast will be easy, “rain and thunderstorms today”.

That would be kind of like a real patient walking into the
doctor’s office with an open fracture of the lower leg. The diagnosis is easy,
“your leg is broken”.

Most days though, my patient’s condition requires further diagnosis
and testing, as I’m sure it is with many doctor’s patients. Whenever the
complaints and symptoms are quite subtle or perhaps very complicated, then an
accurate diagnosis becomes more difficult. The same is true with the weather.

That’s when the doctor sends you for the blood tests, the
x-rays, the MRI’s, the colonoscopies (ugh!), or whatever other tests are
necessary to help make a better diagnosis of your problem and how to treat it. That
is when I head to the computer models, to help guide me towards making a
decision about what the weather is going to do.

Sometimes, the final prognosis, meteorologically or
medically, is more of a guess. An educated guess, based on your training,
experience and how often you have seen these same conditions.

Probability

The doctor might tell me that after surgery, that I might
have a 50/50 chance of surviving. Like
the doctor’s prognosis, weather forecasts are also an expression of
uncertainty. Probability of precipitation may be the most looked-at part of any
weather forecast, but I imagine it is also the least understood.

Probability in a forecast is usually expressed in percent, 30-percent
chance of showers, a 60-percent chance of thunderstorms, etc. etc. But what
does that really mean?

Probability of precipitation is an expression of two
factors: Confidence and Area.

How confident is the forecaster, or the computer model, that
precipitation could actually occur, and over how much of the forecast area will
it occur, if it does.

Case1: The forecaster is very confident, 100-percent, that measurable
precipitation will occur, but it may not occur everywhere within the forecast
area, such as Teton County, as an example. That might generate a 50% probability
of precipitation (PoP).

Case 2: The forecaster’s confidence that measurable rain
will occur is not that high, say 50-percent confidence, but if it does rain, it
would rain over the entire forecast area. That would also generate a 50-percent
PoP.

The problem is, you don’t know which case was used for the
forecast. Which doesn’t really make this any less confusing or misleading, does
it?

Given that, I would say that the best way to interpret these
examples is to say: “There is a 50-percent chance that precipitation could
occur at any point within the forecast area, during the forecast time period”.

A “50-percent chance of rain” does not mean that it will
rain over half of the time period, or over half the forecast area. Which is a
common misinterpretation of PoP.

The table compares the percentages to the uncertain terms
and the alternate descriptors used in most forecasts, to give you a reference
to work from when making decisions about what that forecast really means.

Remember, the forecast is just guidance, like your doctors
advice. In some cases, it may or may not rain, and you may or may not die.

Note: My apologies to any doctors reading this, I did not
mean to imply that weather forecasting was as easy as brain surgery.

Monday, September 14, 2015

It seems
like weather predictions for the coming winter are beginning earlier and
earlier every year. They used to come out in early October, then it was
September, now they are appearing in mid-August.

The early
release of the Old Farmer’s Almanac hit the major media a couple weeks ago. You
can buy it in stores beginning this week. Or, if you have to write a column
about it, like me, you could buy the pre-release digital copy.

It seems odd
to me to be previewing the winter, when I haven’t even had the chance to review
the summer. After all, fall doesn’t officially begin for another three weeks.
But, here we go!

Outlooks
Galore

The various
Farmer’s Almanacs are just one way to get a leg-up on what the winter might be
like. The Climate Prediction Center, a division of NOAA and the National
Weather Service is another source.

El Nino
has dominated the weather limelight this summer, and certainly the current and
predicted state of the El Nino weighs heavily in the long-range outlooks for
this winter. You can get updated on what I wrote recently about El Nino by
searching the archives on the JH News and Guide website, or on my
mountainweather blog page.

The short
story is, it looks like the current El Nino will continue through the winter
and early spring. NOAA expects it to become stronger and peak in November or
December. Previous strong El Nino events
have brought above average snowfall to the Sierras and the Southwest United
States.

NOAA-CPC

I
analyzed all of the long-range outlooks from the Climate Prediction Center
(CPC) for the winter months, broken down into three overlapping three-month
categories, namely: November-December-January, December-January-February, and
January-February-March. I also compared what is known as their “Three-Class”
version and their new experimental, and as yet “unofficial”, “Two-Class”
version of these outlooks. I like the new 2-class version, because it is
simpler and less ambiguous than the 3-class version.

Basically,
the 2-class version establishes what is “normal”, or average, by using historic
weather data from 1981-2010. They pick out the coldest and the driest 15 years,
and the warmest and the wettest 15 years. From there, forecasters then estimate which
regions of the country they believe will be well above or below these averages
and assign probabilities.

For
instance, a 60-percent probability that it will be warmer than normal, means
there is a 40-percent probability temperatures could be below normal. If they
are unsure, then it is a coin-flip, 50/50 chances of being above or below, or
what they call EC “Equal Chances”.

Suffice
it to say; no matter how you slice it, all versions of the CPC outlooks are bleak
for the Northern Rockies. The overall picture they are painting for our area is
for warmer than normal temperatures and below normal precipitation from
November through March. However, the probabilities of that happening are
generally around 60-percent. Doesn’t that give us a 40-percent chance of it
going the other way, colder and snowier? Think positive!

Farmer’s

When I
opened up my digital version of the Old Farmer’s Almanac, the familiar yellow-jacketed
almanac you’ll see in Stone Drug or in your favorite grocery store this week, I
found that it doesn’t do us any favors either. Their big color map of the U.S. has
all of Idaho, Utah, western Montana, western Wyoming and western Colorado
categorized as, “Mild and Dry”.

This
almanac’s forecast has the Cascades of Washington, Oregon, and northern
California under, “Cold and Snowy”. Should I pack my bags for Mt Baker or Mt.
Hood? Not so fast.

In the
2016 edition of the Farmer’s Almanac, the orange and green-jacketed almanac,
they are calling for, “Very Snowy and Typical Winter Cold” for Montana,
Wyoming, and Colorado. Bingo! Let’s run with that forecast, it sounds so much
better than the doom and gloom of all the others.

Caveat
Emptor

Buyer
beware! These are long-range outlooks, which I would liken to reading a fairy
tale. Good or bad, it does not necessarily mean the predictions will come true.

Computer
models generate much of what goes into these forecasts. I work with computer
models everyday, and I can tell you that there are plenty of days that the
models can’t get it right, for just 24-hours into the future. Naturally, I am a
little skeptical of any model that predicts weather conditions 3 to 6 months
into the future.

Take a
deep breath, don’t worry, be happy, it will get cold this winter and it will
snow. Some winters are better than others, and I would never write this one off
before the first snowflake has even had a chance to fall.

NOAA Climate Prediction Center
Three-Month Outlooks

Three-Month Period

Temperature

Precipitation

NOV-DEC-JAN

55% above

55% below

DEC-JAN-FEB

60% above

65% below

JAN-FEB-MAR

50% above

60% below

Probabilities from the new Experimental “Unofficial”
Two-class Climate Outlooks

Jim is the
chief meteorologist at mountainweather.com and has been forecasting the weather
in Jackson Hole and the Teton Mountains for almost 25 years.

Monday, August 31, 2015

(Note: The article in this post was originally published in the Jackson Hole News and Guide on August 19, 2015).The
comments and questions are starting to come more often now, about the current
El Nino and how it will affect our winter. I blame the bigger media outlets for
creating this hype, by attaching monikers to their headlines like: “Super El
Nino”, “Strongest El Nino Ever”, and my personal favorite, “The Great Godzilla
of an El Nino”.

It makes me
want to throw-up when I read these headlines, especially since nothing
extraordinary is actually happening yet.

To help
squelch some of the hype, by way of plain-old scientific explanation, in this
week’s column I am going to tell you what El Nino is, what the current and
forecasted state of the El Nino is, and what affects this El Nino might have on
weather patterns this winter. In particular, what it might mean for snowfall in
Jackson Hole.

El Nino
Defined

El Nino is
not a monster storm, nor is it a series of monster storms that guarantee copious
amounts of snow. I will guarantee you though, that every single major weather
event that happens between now and next spring will be blamed on El Nino.

El Nino is
part of a larger phenomenon that has to do with the Sea Surface Temperature (SST)
in the equatorial Pacific, collectively known as “ENSO”, or the El Nino
Southern Oscillation.

ENSO comes
in three different flavors: 1) El Nino, when SSTs are warmer than average. 2)
La Nina, when SSTs are cooler than average. 3) Neutral (No-Nino), when SSTs are
near average.

The
strength of an ENSO event is measured by how much warmer or cooler those SST’s
are getting, and how far across the Equatorial Pacific they are spreading. This
in turn creates differences in pressure across the Equatorial Pacific. Sometimes,
in the case of an El Nino, a complete reversal of the normal wind flow pattern may
occur.

Ocean temperatures
down near the equator are relatively warm to start with, but during an El Nino
they may get 1 or 2 degrees warmer. This creates more thunderstorm activity
over the ocean, and the effects of that extend up into the upper atmospheric
circulation, as well. And voila, we have
a disruption of the “normal” atmospheric circulation, which translates to a
change in the weather patterns both north and south of the Equator.

El Nino
2015

I don’t
know if you remember back to May of 2014, but NOAA scientists then were
predicting that a “Super El Nino” would develop for the fall and winter of
2014-15. That never materialized. El Nino conditions (warmer SSTs) never showed
up until March of 2015, too late to disrupt winter weather patterns in the
northern Pacific.

May-June-July
2015 average SSTs warmed up to 1-degree (Celsius) above the average in some
portions of the ocean. Winds were not reversing yet, but they were slowing
down, and more convection was noted; that is, more thunderstorms were showing
up on the satellite photos.

All of that
has led NOAA forecasters to predict: “This El Nino will peak in the late
fall/Early winter with 3-month average SSTs near or exceeding 2-degrees C above
normal. IF this forecast comes true, it will place the 2015 event among the
strongest El Ninos in the historical record (1950-2015).”

The strongest
El Nino winters on record were 1997-98, which peaked at 2.3 –degrees above
normal, and 1982-83, which peaked at 2.1 degrees above normal, for their three
month average SSTs in November-December-January.

What’s
Expected?

If this
does develop into an El Nino of those proportions, then what should we expect
to happen? Usually during El Nino winters the jet stream, or storm track, tends
to dip further south in the Northern Pacific, moving over California and the
Southwestern United States, then cruising across the Southeastern U.S., keeping
those locations wetter than normal in winter.

In both
1997-98 and 1982-83 the Sierra Nevada Mountains in California had huge winter
snowfalls, both were attributed to the strong El Nino.

The Pacific
Northwest and northern Rockies are a bit too far north of the storm track
during strong El Nino’s to reap the same benefits. The opposite though is true
during strong La Nina winters, when the storm track usually does favor the Pacific
Northwest and Jackson Hole, and leaves California and the Southwest dry.

In Jackson,
during the strongest El Nino Winter of 1997-98 we had average snowfall in town
and just above average snowfall in the mountains. In the El Nino Winter of
1982-83, we had below average snowfall, both in town and in the mountains.

When I take
into account all the El Nino years, weak & strong, it’s a 50/50 proposition
for Jackson Hole. Half the El Ninos ended up with above normal snowfall around here,
half had below normal snowfall.

Given all
that info, I wouldn’t get too hyped-up about this “Giangundous El Nino 2015”
just yet for Jackson Hole, it might make for a bigger snowfall winter here or
it might not. Unless you live in Tahoe, then it’s going to be HUGE, for sure,
dude!

Jim is the
chief meteorologist at mountainweather.com and has been forecasting the weather
in Jackson Hole and the Teton Range for almost 25 years.

Tuesday, July 28, 2015

An unusually cold Low pressure system for late July moved across the Northern Rockies on Monday, July 27th, 2015 , bringing with it a dramatic drop in temperatures, and snow to the higher elevations of the Teton Range in western Wyoming, as well as some strong, gusty winds.

SNOWSnow was observed at the top of Teton Pass Monday evening, at an elevation of just over 8400-ft. Snow was on the ground down to around the 9500-ft. elevation on Tuesday morning in the Tetons. It is not especially unusual in the higher Tetons to have snow in July, however, to see it on the mountains to such a low elevation this time of year it is. Last summer it snowed down to about the same elevations in late August. So, we are a month earlier this year!

WIND
There were some strong gusty winds with that front, hitting 70 mph at the Lower Saddle (11,610-ft.), 54 mph on top of the JH Tram (10, 318-ft.), and 49 mph over on Lava Mountain near Togwotee Pass (10, 430-ft.).
The Jackson Hole Airport experienced wind gusts of 30 to 40+ mph between noontime and 3:00 pm. They maxed out with a 43 mph gust.

TEMPS
Temperatures dropped over 20 degrees in the valley as the front passed in the afternoon, going from a highs in the mid to upper 60's around noontime to the mid to upper 40's by 3:00 pm.

The low temp at the JH Airport Tuesday got down to 30-degrees. In town it was mid 30's and not really threatening the record low of 31 degrees for July 28th, set back in 1940. The record low for July 29th is 27 degrees, and I have foretasted a low near 30 for Wednesday morning.

In the mountains temps went from a high near 70 degrees at 10,000-ft. on Sunday afternoon to highs in the upper 50's at noontime Monday, then the temperature plummeted to near 30 degrees by 3:00 pm Monday afternoon. A 40-degree drop in about 24-hours!

At one point Monday evening at the Lower Saddle of the Grand Teton, the temperature was 25 degrees and the wind was blowing steady at almost 40 mph, causing the windchill factor to make it feel like 7 degrees. Yes, seven!

Summary of Weather Events around Jackson Hole & the Teton Mountains for July 27th, 2015.